Fault Current Negative Contribution Method for Inverter-Based Distributed Generators Under Grid Unbalanced Fault

With the rapid increase of embedded inverter-based distributed generators (IBDGs), the active distributed network (ADN) is facing security and protection challenges because IBDGs will contribute extra fault current. In contrary to the existing method that IBDGs provide varying degrees of positive contribution to system fault current, in this article, a fault current negative contribution (FCNC) method is proposed for IBDGs to reduce the system fault current lower than the situation where without IBDGs embedded. In the proposed method, a maximum current phase angle adjustment (MCPAA) strategy is conducted for IBDGs to maximize its negative contribution, thus to minimize the system fault current. In order to obtain a more precise current phase angle, a voltage phase angle determination (VPAD) strategy is also formulated by considering the voltage angle difference on the electrical distance between IBDGs and fault bus. Extensive tests and relevant results have validated the feasibility of FCNC method to achieve a negative contribution of IBDGs on system fault current.